This adds a new policy rule which defaults to behave in a
backward compatible way, but will allow operators to enforce
that servers created with a zero disk flavor must also be
volume-backed servers.
Allowing users to upload their own images and create image-backed
servers on local disk with zero root disk size flavors can be
potentially hazardous if the size of the image is unexpectedly
large, since it can consume the local disk (or shared storage pool).
It should be noted that disabling the new policy rule will
result in a non-backward compatible API behavior change and no
microversion is being introduced for this because enforcement via
a new microversion would not close the security gap on any previous
microversions.
Related compute API reference and user documentation is updated
to mention the policy rule along with a release note since
this is tied to a security bug, which will be backported to stable
branches.
Conflicts:
nova/policies/servers.py
nova/tests/unit/test_policy.py
NOTE(mriedem): The conflict is due to not having change
Iedd3fea0e86648fae364f075915555dcb2c4f199 in Queens for trusted
certs.
Change-Id: Id67e1285a0522474844de130c9263e11868f67fb
Closes-Bug: #1739646
(cherry picked from commit 763fd62464)
7bcd581c78